Selector

ABSTRACT

A device for selection of elements of air conditioning installations in a form similar to a slide-rule.

United States Patent Ell 51 Apr. 15, 1975 SELECTOR [56] References Cited [76] Inventor: William M. Ell, 5513 Trent Cl. Apt UNITED STATES PATENTS 21], Alexandria. Va. 223ll 2.1 l8.773 5/1938 Ball 235/83 2,142,593 1/1939 Woodling t 235/6l B [221 May 2,892.586 6/1959 Graham 4 l 235/6l GM 2 Appl 467 5 0 3.347.459 lO/l967 Thicl......... 235/6l NV 3.784.797 l/l974 Kmll 235/88 Related U.S. Application Data [63] Continuation of Ser. No. 367.412, June 6. I973, Primary ExaminerLawrence R. Franklin a andon d- Anorney, Agent. or Firm-Frederick W. Turnbull [52] U.S. Cl 235/83; 235/88 57 ABSTRACT [5 l] Int. Cl G06c 3/00 A device for selection of elements of air conditionin 8 Fleld of Search B, GM, installations in a form to a slide mle- 8 Claims, 5 Drawing Figures 'ATENTEEAFR 1 5%375 SHLEI 1 0f 5 EVAPORATOR CAPACITIES (52,000 THRU IO2,000)

van-0500 COPELAND COPELAND pram-0750 z. AmOP mO1 w IQ mommwmaioo ".0 53.40 92450212 ms Nl HBSNHONOO :IO AilQVdVO OIWVNAOOWHBHL SELECTOR This application is a continuation of application Ser. No. 367.412 filed June 6, 1973 now abandoned.

The device comprises a flat base carrying appropriate numerals and curves and at least one pivoted radial arm carrying appropriate indicia as well as carrying a fixed and a movable pointer.

It is a primary object of the invention to provide a device by which selections can be quickly and easily made of a compressor and a matching condenser for an air conditioning system using a preselected evaporator.

Another object of this invention is to provide a device that is of such configuration and light weight that it can be carried in a briefcase.

Another object of this invention is to provide a device that has a minimum number of movable parts.

Another object of this invention is to provide a selector of the character described that is designed so that one can quickly determine the percentages of rated capacity at which an element of an air conditioning circuit is to be used.

Another object of this invention is to provide a selector of the character described whose faces may be provided with a plurality of removable and replaceable charts as desired as well as having more than one arm on each face.

Other and further object and advantages will appear from the following specification taken with the accompanying drawings in which like reference characters refer to like parts in the several views and in which:

FIG. 1 Plan view of the device.

FIG. 2 Enlarged perspective ofa fragment of the pivoted arm.

FIG. 3 Perspective view of one form of the device.

FIG. 4 Diagram of an air conditioning circuit.

FIG. 5 Plan view of another form of the device.

There are many charts and graphs available from which the necessary information required in designing an air conditioning system can be found. such as for "Evaporator Correction Factors" in which refrigerant temperatures are plotted on rectangular coordinates against correction factors" which represent percentages of the rated capacities of evaporators', compressor charts providing constant temperature lines in terms of BTUH plotted in rectangular coordinates against refrigerant inlet temperatures corresponding to the tem perature found in the evaporator correction factor" charts; and similar tables and charts relating to condenser characteristics. Using such charts. tables. and graphs, which are on rectangular coordinates. it is necessary to refer to many different ones. and to consult handbooks and the like in order to arrive at the answers as to which compressor of several having different capacities should be selected. and which condenser should be selected to receive the refrigerant from the selected compressor. The device of the present invention has combined the information from such Tables and Charts in a manner such that. by simple manipulation of the device, the best choice of equipment may be arrived at in connection with the selection of a compressor and a condenser to operate with a preelected evaporator.

It is noted also that after having determined the BTUH that must be removed from the air to be cooled by the evaporator, it is known that the evaporator should be selected to operate preferably so that the refrigerant temperature entering the compressor will usually not fall below 39F (or 40F). preferably between 39 and 48F. so the correction factor" will be between 0.6 and 1.0. referring to a wet bulb temperature" of 67F for the air to be cooled.

Directing attention first to FIG. 3 of the drawings. it will be seen that this invention consists of a flat base I0 that carries on its face indicia including numerals along one edge starting from a point of origin from which an arm I2 extends radially outward from a pivot 14 at the origin fixed to the base 10. There may be two arms I2 and 12a. being located on the opposite side of the base II) as seen in phantom in FIG. 3. The two arms 12 and 12a would then be secured to the base by the common center pin 14. Legs 16 may be provided to support the device on a table top. Curves 28 and 280 as well as curves 30 and 30a and further numerals as explained below appear on the surface of base III.

In FIG. 1 of the drawings it will be seen that arm I2 is offset so that one edge lies on a radius from pivot 14. The arm is provided with two scales I8 and 20 and a slider 22 that is provided with a pointer 24. as illustrated in FIGS. 1 and 2 of the drawings. A fixed pointer 26 is provided on scale 20 indicating a temperature of 39F. and also indicating I00" or a correction factor of 1.0) on scale I8.

It will be noted that FIG. 1 illustrates the structure of the invention. The face of the base I0 is provided with at least two groups of curves. One group of curves 28 and 280 relating to compressors for use with the half line" scale on radius I4-A, and the other set of curves 30 and 30a being for use with a scale on line A-B. both scales being expressed in B.T.U.H. and both used in conjunction with the radial scales and the pointers on pivotable arm 12 as more fully explained below.

With respect to the physical construction of the device the materials used may range from paper or bristolboard, to wood. plastic or metal. The numerals. scales, curves. may be printed. etched or engraved on the surface of the planar body of the device to suit the material selected.

Notice in FIG. 1 that scale 20 on the swingable arm I2 is in degrees Farenheit from 39F at the fixed pointer 26 to perhaps 48F toward the pivot. and the second scale 18 is in percentages from I00 percent at fixed pointer 26. If this percentage scale were continued it would extend to 0 percent at pivot I4. These percentages represent the correction factor for the evaporator to be used. and also the actual percentage of the distance from pivot I4 to fixed pointer 26, which is I00 percent, and so represents the percentage of the rated capacity of the evaporator at which it will be used.

In air conditioning design it is necessary to compute the capacity of an evaporator. according to the climatic conditions. the estimated heat loss of the structure. the frequency of computation and closing the doors and so forth. Once this conputation has been completed the designer chooses an evaporator (cooling coil) which. in use. will remove the required B.T.U.H. from the air to be cooled, at less than the I00 percent full rated capacity of the evaporator.

Starting with the evaporator unit E in FIG. 4, the air conditioning circuit includes piping to lead the refrigerant, which has removed heat from the space to be cooled by the evaporator E, to a compressor C where the refrigerant is heated due to being compressed and also incidentally further heated by the compressor due to friction. etc. Then the refrigerant is conducted to a condenser D where the heat both from the space being cooled and that added by the compressor is removed and the refrigerant is liquified. A capillary tube or an expansion valve F leads the liquid refrigerant from the condenser back to the evaporator where. upon vaporizing again. it takes on heat from the space to be cooled. The circuit is therefore complete and closed.

Evaporators are rated" according to the B.T.U.H. they can remove when the temperature of the refrigerant leaving the evaporator is at a designated temperature. This temperature is. at present. conventionally set at 40F. If the temperature change of the refrigerant leaving the evaporator is less than it would be if the evaporator was operated at I percent of the "rated capacity. the percentage of the rated capacity actually used is termed the correction factor."

In this disclosure the "correction factor" is in reference to a wet bulb temperature of 67F indoor temperature entering the evaporator. Some modifications of the device would be required if other wet bulb temperatures are referred to.

The higher the temperature at which the compressor receives the refrigerant the higher the temperature the refrigerant will have as it leaves the compressor. The refrigerant leaving the compressor must be at a pres sure (and temperature) such that. when cooled in the condenser. it will liquify so that when returned to the evaporator through the capillary tube (or expansion valve) it can. as it evaporates (vaporizes). absorb the heat necessary to be taken from the air to be cooled which is circulated through the evaporator.

Compressors are designed to take refrigerant at temperatures. from slightly less than the conventional datum temperature of 40F. to temperatures somewhat higher. and compress the refrigerant to a temperature of desirably between land 145F. The compressor manufacturers each supply data for each of the compressors they sell. From such data. constant discharge temperature curves (l. 130, and 140F. etc.) for each compressor may be plotted (indeed are plotted on normal graph paper having rectangular coordinates). These curves must be modified for use in the present invention.

The heat added to the refrigerant by the compressor will need to be removed from the refrigerant by the condenser. Here. if the refrigerant from the compressor is at a constant temperature (125, 130, 140?) the B.T.U.H. removed by the condenser will be a function of the volume and temperature of the refrigerant coming to the compressor. and the volume and temperatue of the coolant for the condenser. Condensers are designed to be able to condense the refrigerant using either ambient air. or water under estimated adverse conditions.

In FIG. 1 we notice the halfline" from the pivot 14 along a radius I4-A that carries legends indicating B.T.U.H. rated evaporator capacities. From the manufacturers data relating to the type of evaporator to be used. it is known what the correction factors for that type of evaporator are, and that. at each correction factor. the temperature of the refrigerant leaving the evaporator will have a fixed value. The scales l8 and 20 embody this knowlwdge.

It is known that a compressor receiving refrigerant vapor at a fixed temperature will, in the process of compressing it. add considerable heat to the refrigerant so that. when the refrigerant is discharged from the compressor. it will be at quite a high but fixed temperature. It has been determined that discharge temperatures from a compressor may conveniently be from to I50F. A compressor that will receive the refrigerant at the temperature at which it is discharged from the evaporator and discharge it at a temperature between 120 and l50F will then be selected. Since a fixed temperature output from the compressor corresponds to a fixed input temperature. constant temperature curves may be established as. indeed. are conventionally provided on rectangular coordinates by the compressor manufacturers.

The constant temperature curves seen at 28 in FIG. 2 are modifications of the conventional constant temperature curves as they are plotted using a scale in B.T.U.H. along the fixed half line" extending radially from the pivot l4-A and radial swingable scales l8 and 20 on arm 12. The two scales 18 and 20 refer to the correction factor and to the temperature at which the refrigerant enters the compressor respectively.

It is well known that with a smaller compressor less refrigerant can be compressed than with a larger one. so. in selecting a compressor for 30,000 B.T.U.H. it would be smaller than one selected for 90,000 B.T.U.H. (Note constant temperature lines 280 on FIG. 1). Each compressor. however. has a range within which its operation will be satisfactory. Quite similar compressors. manufactured by competing companies. may have overlapping ranges of satisfactory operation. The capacity legends along the half line of the quadrant of FIG. 1 may be added to indicate limits of satisfactory operation of named equipment.

The curves 28 seen in the quadrant of FIG. I that are labeled and are constant temperature curves reporting the discharge temperature from a specific compressor at different loads. Two compressors with overlapping areas of satisfactory operation will have similar. but somewhat differently located curves for the same temperatures. Such similar curves. if-

widely separated as curves 28 and curves 280 may be in the same quadrant but may also be printed in different colors so as to be readily distinguished. If they would lie fairly close together in one quadrant. they may not be placed on a different quadrant, as for instance on the opposite face of base 10, which is one explanation 0f the desirability of more than one quadrant as suggested in FIG. 5. Where several colors are used in a single quadrant. the color differences may be accentuated in a known manner by appropriate transpar-- ent color filters.

The expressions thermodynamic circuit or air conditioning circuit" refers in this application to any closed circuit where vaporization and condensation are the made of transferring heat whether for heating or cooling and Refrigerant" is used herein to refer to a heating medium as well as to a cooling medium.

We will assume we have selected an evaporator. hav' ing a rated capacity of ll5.000 B.T.U. at the datum temperature. As indicated in the air conditioning system circuit chart FIG. 4, for which we wish to select an appropriate compressor. we notice that the actual heat to be absorbed by the evaporator is 9l.l00 B.T.U.H. in the FIG. 4 example.

When the compressor has been properly selected. the constant temperature line (of that compressor) through the movable pointer 24 will need to fall within an acceptable range. preferably between I25 and 1440F (except in special cases) when the movable pointer 24 indicates an acceptable correction factor.

The temperature of the refrigerant delivered to the compressor is indicated by the position of the movable pointer 24 along the temperatue scale on the pivoted arm. The temperature at which the refrigerant leaves the compressor is indicated by the constant temperature curve (curves 28) on which the movable pointer rests when the proper compressor is selected. From FIG. I we see that this temperature in the example of FIG. 4 is 130F.

To complete the circuit for the refrigerant so that the condensed refrigerant can be again expanded in the evaporator, it is necessary to remove from the refrigerant the heat it absorbed during evaporation and the heat added to it by the compressor.

Considering FIG. 4 we therefore assume that the installation under consideration requires the removal by evaporator of 9l.l00 B.T.U.H. under its full load conditions (perhaps at an ambient outdoor temperature of 95F). In order to provide for the 9l,l00 B.T.U.H. it is necessary to provide an evaporator of "rated" capacity greater than 9l.l00 B.T.U.H. It is usual to select an evaporator such that it will be operating at between 65 percent to 90 percent of rated capacity (correction factor) when operating under the most extreme conditions expected. It is seen from FIG. I that with an evaporator having a rated capacity of l l5.000 B.T.U.H.. when the fixed pointer 26 on the scales l8 and 20 is set on the line opposite I l5,000, on the half line l4-A of the chart. the 9l,l00 B.T.U.H. line will cross scale 18 on arm I2 at a little under 80 percent of the rated" capacity of the evaporator. From scale 20 on arm I2 it is found that when used under these conditions. the temperature of the refrigerant as shown by the scale as being at 45F which is in fact the temperature of the refrigerant entering the compressor, a lF drop in temperature has occurred between the evaporator outlet and the compressor.

In choosing a compressor to match the evaporator we see that the point at the intersection of the line 9l,l00 B.T.U.H. and the radial arm falls between the I40 and the lF constant temperature curves 28 (at which the refrigerant will be delivered from the compressor to the condenser) for a compressor Copeland PRAI- 0750. In fact. the intersection falls on the l30F line for this compressor which is entirely suitable. This compressor is therefore selected. (The compressor here referred to is an actual compressor that is on the market).

We see another set of constant temperature curves 28a for a compressor Copeland VREl-OSOO." It is at once clear that this latter compressor would not be suitable for use in the air conditioning circuit under consideration.

We notice in the quadrant of FIG. 1 a group of constant temperature curves 30 and 300 which may be termed condenser selecting curves, similar to the curves that have been discussed above but lying generally parallel to the half line l4-A on the quadrant. The temperature limits to be considered are again perferably from l25 to 145F which is the temperature determined by use of the first set of curves 28 or 280. The temperature at which the expanding gas is delivered to the compressor has been determined by the location of the movable pointer measured against the temperature markings 20 on the pivotable arm; the temperature of the refrigerant passing from the compressor to the evaporator is determined from the set of constant tem' perature lines 28.

If. then. the arm is swung, keeping the movable pointer in place on the arm at its selected reading on scales l8 and 20 until it falls on the constant temperature line of the condensor selecting curves 30 corresponding to the temperature at the compressor outlet as determined above (i.e.. the compressor constant temperature curves 28) the necessary condenser capacity can be read off from the capacity legends on the condenser capacity line AB in FIG. I opposite the mov able pointer.

It will be noted that the constant temperature lines in both cases are plotted in one direction against a straight fixed line, on the planar chart and in the other direction along a radial movable coordiante. Interpolation may be necessary where temperature fall between the temperature curves or between markings along the arm.

It will be noticed that it is preferred that several similar quadrants be provided. This does not appear to be a technical requirement but rather a practically desirable feature especially in view not only of differences between makes and model of equipment, but also because of different climatic conditions. and perhaps because of differences in the coolant (water or air) used to remove the heat from the condenser. or in differences in the specific refrigerant used. The device of the present invention, therefore. gives not only a basic tool to be used in selecting components for use in any air conditioning system. but. by adjusting the curves in order to take into consideration correction factors. it assures less chance of mistake. Also. it is clear. if second hand equipment of known capacity is available. that the calculator of this invention can be used to determined the necessary characteristics of other components in order to reuse the second hand component.

Various changes and modifications can be made in the device of this disclosure without departing from the scope of the invention as defined by the following claims.

I claim:

1. A selector for selecting a second thermodynamic element for use with a preselected first thermodynamic element ofa thermodynamic circuit. such as an air conditioning installation, by reference to the B.T.U.H. capacities of and/or temperatures to and from the thermodynamic elements: said selector comprising a planar chart including indicia along at least one half-line extending from a point of origin, the indicia expressing the thermodynamic capacities in B.T.U.H. from 0 at said point of origin to a maximum for any selected first thermodynamic element for which a suitable second thermodynamic element is to be selected. at least one set of constant temperature curves on said planar chart each line of said set of lines representing an acceptable temperature of discharge of the refrigerant from said second thermodynamic element. at least one pivotable radial arm extending from a pivot at said point of origin and of a length at least equal to said half-line, a datum point on said radial arm indicating percent of the distance from said point of origin to the indicia expressing the maximum rated capacity of any first thermodynamic element that may be preselected. a first scale of indicia extending along said radial arm from said datum point indicating percentages of the distance from said point of origin to said datum point. said datum point also indicating. on a second scale along said pivotal arm a datum temperature at which refrigerant from said first thermodynamic unit enters said second thermodynamic unit at the rated" capacity of said first thermodynamic unit. said second scale along said radial arm indicating temperatures of the refrigerant entering said second thermodynamic element from said first thermodynamic element when used at percentages ofthe rated capacity of said first thermodynamic element as indicated on said first scale; whereby it may be determined by pivoting said arm to place the datum point on the line normal to said half line opposite the indicia thereon indicating the rated thermodynamic capacity of said first preselected thermodynamic element. whether the second thermodynamic element represented by said set of constant temperature curves will be suitable for use with said first thermodynamic element 2. The selector of claim 1 including a plurality of sets of constant temperature curves each for a second thermodynamic element that might be suitable for use with one or another preselected first thermodynamic element.

3. The selector of claim 1 including also at least one set of thermodynamic indicia on a line normal to said half-line expressed in B.T.U.H. referring to the thermodynamic capacities of a third thermodynamic element to receive the refrigerant from said second thermodynamic element. and at least one set of constant temperature curves each line of said set of constant temperature lines representing the temperature of the refrigerant received by said third thermodynamic element from said second thermodynamic element. whereby the suitability of said third thermodynamic element for use with said second thermodynamic element may be determined.

4. The selector of claim 3 in which there are two sets of thermodynamic indicia expressed in B.T.U.H. on the line normal to said half line and at least one set of constant temperature lines associated with each said set of thermodynamic indicia representing the temperature at which the refrigerant is received by said third thermodynamic element from said second thermodynamic element. whereby the suitability of third thermodynamic elements represented by each said set of constant temperature lines for use with a second thermodynamic element may be determined.

5. The selector of claim 3 including a plurality of sets of constant temperature curves representing the temperature of the refrigerant received by said third thermodynamic element, one said set referring to an air cooled said third thermodynamic element and another set referring to a water cooled said third thermodynamic element.

6. The selector of claim 1 in which said planar chart includes a plurality of half-lines extending from said point of origin, and a plurality of pivotable arms are provided, the constant temperature curves associated with each of said half-lines referring to different second thermodynamic elements.

7. The selector of claim 6 in which the data referred to by one half-line and one pivotable radial arm refers to a different refrigerant than referred to by the data referred to by a second half-line and pivot-able radial arm.

8. The selector of claim 6 in which at least one set of thermodynamic indicia expressed in B.T.U.H. referring to the thermodynamics capacities of a third thermodynamic element are provided on a line normal to each said halfdine, and at least one set of constant temperature curves each line of each said set of constant temperature lines representing the temperature of the refrigerant received by a said third thermodynamic element from said second thermodynamic element.

i i i 

1. A selector for selecting a second thermodynamic element for use with a preselected first thermodynamic element of a thermodynamic circuit, such as an air conditioning installation, by reference to the B.T.U.H. capacities of and/or temperatures to and from the thermodynamic elements: said selector comprising a planar chart including indicia along at least one half-line extending from a point of origin, the indicia expressing the thermodynamic capacities in B.T.U.H. from 0 at said point of origin to a maximum for any selected first thermodynamic element for which a suitable second thermodynamic element is to be selected, at least one set of constant temperature curves on said planar chart each line of said set of lines representing an acceptable temperature of discharge of the refrigerant from said second thermodynamic element, at least one pivotable radial arm extending from a pivot at said point of origin and of a length at least equal to said half-line, a datum point on said radial arm indicating 100 percent of the distance from said point of origin to the indicia expressing the maximum rated capacity of any first thermodynamic element that may be preselected, a first scale of indicia extending along said radial arm from said datum point indicating percentages of the distance from said point of origin to said datum point, said datum point also indicating, on a second scale along said pivotal arm a datum temperature at which refrigerant from said first thermodynamic unit enters said second thermodynamic unit at the ''''rated'''' capacity of said first thermodynamic unit, said second scale along said radial arm indicating temperatures of the refrigerant entering said second thermodynamic element from said first thermodynamic element when used at percentages of the rated capacity of said first thermodynamic element as indicated on said first scale; whereby it may be determined by pivoting said arm to place the datum point on the line normal to said half line opposite the indicia thereon indicating the rated thermodynamic capacity of said first preselected thermodynamic element, whether the second thermodynamic element represented by said set of constant temperature curves will be suitable for use with said first thermodynamic element.
 2. The selector of claim 1 including a plurality of sets of constant temperature curves each for a second thermodynamic element that might be suitable for use with one or another preselected first thermodynamic element.
 3. The selector of claim 1 including also at least one set of thermodynamic indicia on a line normal to said half-line expressed in B.T.U.H. referring to the thermodynamic capacities of a third thermodynamic element to receive the refrigerant from said second thermodynamic element, and at least one set of constant temperature curves each line of said set of constant temperature lines representing the temperature of the refrigerant received by said third thermodynamic element from said second thermodynamic element, whereby the suitability of said third thermodynamic element for use with said second thermodynamic element may be determined.
 4. The selector of claim 3 in which There are two sets of thermodynamic indicia expressed in B.T.U.H. on the line normal to said half line and at least one set of constant temperature lines associated with each said set of thermodynamic indicia representing the temperature at which the refrigerant is received by said third thermodynamic element from said second thermodynamic element, whereby the suitability of third thermodynamic elements represented by each said set of constant temperature lines for use with a second thermodynamic element may be determined.
 5. The selector of claim 3 including a plurality of sets of constant temperature curves representing the temperature of the refrigerant received by said third thermodynamic element, one said set referring to an air cooled said third thermodynamic element and another set referring to a water cooled said third thermodynamic element.
 6. The selector of claim 1 in which said planar chart includes a plurality of half-lines extending from said point of origin, and a plurality of pivotable arms are provided, the constant temperature curves associated with each of said half-lines referring to different second thermodynamic elements.
 7. The selector of claim 6 in which the data referred to by one half-line and one pivotable radial arm refers to a different refrigerant than referred to by the data referred to by a second half-line and pivotable radial arm.
 8. The selector of claim 6 in which, at least one set of thermodynamic indicia expressed in B.T.U.H. referring to the thermodynamic''s capacities of a third thermodynamic element are provided on a line normal to each said half-line, and at least one set of constant temperature curves each line of each said set of constant temperature lines representing the temperature of the refrigerant received by a said third thermodynamic element from said second thermodynamic element. 